Hugo Cuéllar Hurtado, accused of being a drug trafficker, said, “I have nothing to hide.”

Rodrigo Cruz for The New York Times

By RANDAL C. ARCHIBOLD

March 25, 2014

TLAJOMULCO, Mexico — The United States calls Hugo Cuéllar Hurtado a longtime trafficker of the cocaine coming from South America, working with one of the men believed to command Mexico’s biggest drug cartel now that its leader, Joaquín Guzmán Loera, has been captured.

But while Mr. Guzmán — known as El Chapo, or Shorty — spent 13 years on the run, sometimes even escaping through underground tunnels dug under bathrooms, Mr. Cuéllar walks freely around Guadalajara, attending luncheons and chatting up diplomats. He says he even won a government grant for an ostrich farm he runs here.

“Let them come and investigate me,” he said leisurely over a breakfast of ostrich steaks and sausages at his 57-acre ranch, which the Treasury Department just designated a money-laundering pit for Mr. Guzmán’s Sinaloa cartel. “I have nothing to hide.”

If arresting the cartel’s leader proved to be a 13-year challenge, requiring extensive cooperation between Mexican and American authorities, then cracking the financial network sheltering the Sinaloa cartel’s money, estimated to be several billion dollars, may be just as tough.

Many of the people and companies suspected of forming the cartel’s extensive money-laundering network continue to operate, even though they appear, as Mr. Cuéllar just did, on the American government’s so-called kingpin list of cartel operatives and their associates.

Like Mr. Cuéllar, businesspeople accused of working with the cartel live openly here and elsewhere in Mexico, despite American assertions that they are helping to hide billions in illicit profits through an intricate web of ranches, pawnshops, jewelry stores, money exchanges, a racetrack, even a day care center that hummed with the comings and goings of children on a recent afternoon. The day care center was added to the sanctions list seven years ago.

While American and Mexican authorities have conducted some joint investigations and seizures, the kind of close collaboration that led to the capture of Mr. Guzmán last month often breaks down when it comes to dismantling the cartel’s financial backbone. American officials say that they identify suspects based on intelligence from drug, customs and immigration agents, but that to their great frustration there is too little follow-through in Mexico to pursue shady businesses and their owners.

“There is not enough emphasis there on making it a priority,” said Alonzo Peña, a former deputy director at Immigration and Customs Enforcement. “It took the U.S. a long time to focus on money. For a long time, it was ‘Let’s just go after the drugs.’ The U.S. has evolved,” he added, while “Mexico is a little behind the curve and has not made as much of a shift from drugs to money.”

Mexico has new laws to fight money-laundering, but a senior Mexican official said the evidence the United States presents often does not rise to a level that would allow property seizures or arrests under Mexican law.

“It’s one thing to designate; it’s another to give proof,” the official said, speaking on the condition of anonymity in order to go beyond official talking points.

Michael S. Vigil, a former chief of global operations at the United States Drug Enforcement Administration, said that when Mexico seized property and assets, they were often returned under a judge’s order, through loopholes exploited by cartel lawyers.

“There has to be a motivation and willingness to work together and go after the assets,” Mr. Vigil said. “The only thing that hurts the traffickers is when you take away their money and property.”

Few people have gone to prison or have had their businesses shut down as a result of the American sanctioning. Instead, analysts said, it functions more as a scarlet letter that can complicate finances by prohibiting American banks, companies and citizens from doing business with them, making cross-border banking difficult and chasing away some legitimate investors.

“The U.S. operations and designations are pretty unilateral,” said Eric L. Olson, a scholar at the Wilson Center’s Mexico Institute. But Mexican officials “don’t have to go along” with the American enforcement actions, he noted.

Even when nations work together, “the ability to shut down the finances of a global operation is pretty difficult,” Mr. Olson said. “It’s one thing to go after an individual business like a shoe repair shop in Querétaro, but to dismantle the overall organization like the Sinaloa operation is global.”

Guadalajara and Culiacán, the capital of Sinaloa State, which both lie in agricultural hubs along drug smuggling routes, are places where Mr. Guzmán is believed to have hidden his cash.

“The city is kept afloat by narco money,” said Javier Valdez Cárdenas, founder of Ríodoce, a newspaper in Culiacán. “The amount of bistros, restaurants, spas, shopping malls, luxury car dealerships, condos — it does not correspond to the life of everyday Sinaloans. It’s the narco presence.”

The Treasury Department says Mr. Cuéllar has been a trafficker for decades, arranging cocaine shipments for Juan José Esparragoza, known as El Azul or Mr. Blue, one of two or three people suspected of leading the cartel after the capture of Mr. Guzmán.

The senior Mexican official declined to comment on Mr. Cuéllar’s case, refusing to say whether his assets were being investigated. Mr. Cuéllar is not known to face criminal charges in Mexico or in the United States, though such charges may be filed under seal and made public later.

The Culiacán auto racing track landed on the Treasury Department’s list in 2011 as a cartel asset. It continues to operate and had a healthy crowd on a recent night for its weekly “arrancones,” or drag racing.

Mr. Cuéllar runs an ostrich farm in his 57-acre ranch in Tlajomulco, Mexico.

Rodrigo Cruz for The New York Times

Joel López, who said he opened the track in 2006, contended that the Treasury Department had wrongly identified a lieutenant of Ismael Mario Zambada — known as El Mayo, another man believed to be a possible successor to Mr. Guzmán — as the controlling investor behind it.

“I am a businessman, and I have nothing to hide,” Mr. López said. “A lot of things are presumed here in Sinaloa, so all the businessmen like myself are exposed to the possibility of being linked to organized crime.”

The exact ownership and profitability of businesses are often difficult to discern. A dairy called Santa Monica, which the United States says is a reservoir for the cartel’s dirty money, had no products available at the largest grocery chain in Culiacán, its home base. In a supermarket where the brand was found, only one product, whole milk, was for sale, compared with an array of milks, cheeses and yogurts from other brands.

At the dairy’s unmarked plant on a highway outside Culiacán, workers said there were no representatives available to talk. At a small administrative office in town, across from an abandoned Santa Monica plant, a receptionist likewise said no owner or manager was available. No one answered a message left there.

Mr. Cuéllar landed on the sanctions list five days after the capture of Mr. Guzmán, part of what American officials call a renewed effort to tighten the financial noose on the cartel. Mr. Cuéllar complained that he now stands to lose American customers and perhaps some Mexican ones, without due process.

Still, his 30-odd workers kept busy, tending the Friesian horses he keeps, feeding a new batch of ostrich chicks and carving meat at the ranch’s processing plant. A grant from the Mexican agriculture department in 2011 helped modernize the facilities, according to Mr. Cuéllar and Mexican newspaper accounts.

Mr. Cuéllar, a Colombian-Mexican, says he is the victim of guilt by association with a childhood friend, Leonidas Vargas Vargas, a Colombian drug lord shot to death in 2009 while serving a 19-year sentence for narcotics trafficking in Spain

“That is the only thing I can think of, that they think I have some link with that guy,” he said.

Five of Mr. Cuéllar’s relatives also face Treasury sanctions, including a son, John Fredy Cuéllar, and a daughter-in-law, Gabriela Amarillas López. Ms. Amarillas is the daughter of Sinaloa State’s under secretary for finance, Gildardo Amarillas López, who has denied any connections to drug trafficking.

If Mr. Cuéllar’s ranch suffers from the American sanctions, he said, he will probably sell it and do something else — another limit of the sanctions. He said he was already considering liquidating some of his assets.

“I guess I would have to find another business,” he said.

Correction: March 25, 2014

An earlier version of this article misspelled the surname of a son of Hugo Cuéllar Hurtado. He is John Fredy Cuéllar, not Cuéller.